McGovern was a bomber pilot in World War II who became an early critic of the Vietnam War and a leader of the Democrats' liberal wing.

He was elected to his first of three Senate terms in 1962.

McGovern ran for president three times, also making a try for the nomination in 1968 and 1984. Despite the 1972 Watergate break-in, Nixon won a second term in one of the biggest landslides in modern history.

Bill and Hillary Clinton said Sunday they were saddened by McGovern's passing. They said in a statement that they met McGovern while campaigning for him in 1972 and their friendship endured for 40 years.

The Clintons said McGovern was "a tireless advocate for human rights and dignity" but of "all his passions, he was most committed to feeding the hungry, at home and around the world."

McGovern collaborated with former Republican Sen. Bob Dole to create an international food for education and child nutrition program, for which they shared the 2008 World Food Prize.